Put the hidden input in the overlayer

The overlayer is absolutely positioned to exactly fill the scroll-view.
If we can retain this strategy and never give the input a position that
exceeds the bounds of the overlayer, we can guarantee that it never
forces the scroll position of the scroll view to change when it is
focused due to the browsers default behavior.

src/editor-component.coffee

@@ -13,7 +13,8 @@ React.createClass
   render: ->
     div className: 'editor',
       div className: 'scroll-view', ref: 'scrollView',
-        div className: 'overlayer'
+        div className: 'overlayer',
+          InputComponent ref: 'hiddenInput', className: 'hidden-input', onInput: @onInput
         @renderVisibleLines()
       div className: 'vertical-scrollbar', ref: 'verticalScrollbar', onScroll: @onVerticalScroll,
         div outlet: 'verticalScrollbarContent', style: {height: @getScrollHeight()}
@@ -25,7 +26,6 @@ React.createClass
     followingHeight = (lineCount - endRow) * @state.lineHeight
 
     div className: 'lines', ref: 'lines', style: {WebkitTransform: "translateY(#{-@state.scrollTop}px)"}, [
-      InputComponent ref: 'hiddenInput', onInput: @onInput
       div className: 'spacer', key: 'top-spacer', style: {height: precedingHeight}
       (for tokenizedLine in @props.editor.linesForScreenRows(startRow, endRow - 1)
         LineComponent({tokenizedLine, key: tokenizedLine.id}))...
@@ -120,7 +120,7 @@ LineComponent = React.createClass
 
 InputComponent = React.createClass
   render: ->
-    input @props.className, ref: 'input'
+    input className: @props.className, ref: 'input'
 
   getInitialState: ->
     {lastChar: ''}